Method for forming an assembly having mating superfinished components

ABSTRACT

A method for forming an assembly having a housing and first and second components. The first and second components are movable relative to one another in the housing. The method includes: providing first and second workpieces; moving the first and second workpieces relative to one another in a predetermined manner that produces relative sliding contact between the first and second workpieces while performing a superfinishing operation on the first and second workpieces to form the first and second components, respectively, wherein the superfinishing operation does not comprise a lapping operation; and mounting the first and second components in the housing such that the first and second components are engaged to one another and are movable relative to one another in the predetermined manner.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 15/846,280 filed Dec. 19, 2017, the disclosure of which isincorporated by reference as if fully set forth in detail herein.

FIELD

The present disclosure relates to a method for forming an assembly thathas mating superfinished components.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

There is a need in the art for a cost efficient method for improving thefinish of the mating surfaces of components that movably engage oneanother in an assembly. For example, power losses through the hypoidgears of a modern automotive driveline component are significantlyaffected by the surface finish of the teeth of the hypoid gears. Theteeth of such hypoid gears are commonly lapped together and as such,have a relatively low surface finish. In such gears, however, furtherimproving the surface finish of the gears can significantly reducesurface friction so that the driveline component is able to operate moreefficiently. Post-lapping processes, such as an Isotropic Superfinishingprocess, have been employed to obtain further reductions in the surfacefinish of hypoid gears, but such post-lapping processes tend to haverelatively low throughput.

Accordingly, it would be desirable to avoid the use of a lapping processwith a subsequent finishing operations to obtain a desired surfacefinish with a desired level or degree of conformity between the surfacesof the mating components.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

In one form, the present disclosure provides a method for forming anassembly having a housing and first and second components. The first andsecond components are movable relative to one another in the housing.The method includes: providing first and second workpieces; moving thefirst and second workpieces relative to one another in a predeterminedmanner while performing a superfinishing operation on the first andsecond workpieces to form the first and second components, respectively,wherein the superfinishing operation does not comprise a lappingoperation; and mounting the first and second components in the housingsuch that the first and second components are engaged to one another andare movable relative to one another in the predetermined manner.

In another form, the present disclosure provides a method for forming anassembly having a housing and first and second components. The first andsecond components are movable relative to one another in the housing.The method includes: mounting a first workpiece for rotation about afirst axis; mounting a second workpiece in meshing engagement with thefirst workpiece and for rotation about a second axis; rotating the firstworkpiece about the first axis to drive the second workpiece about thesecond axis; performing a superfinishing operation on the first andsecond workpieces while the second workpiece is being driven by thefirst workpiece to form the first and second components, respectively,wherein the superfinishing operation does not comprise a lappingoperation; and mounting the first and second components in the housingsuch that the first and second components are meshingly engaged to oneanother and are rotatable relative to the housing about the first andsecond axes, respectively.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is a sectional view of an exemplary assembly constructed inaccordance with the teachings of the present disclosure;

FIG. 2 is a schematic illustration in flowchart form of an exemplarymethod according to the teachings of the present disclosure;

FIG. 3 is a perspective view of a machine for performing a portion of amethod in accordance with the teachings of the present disclosure; and

FIG. 4 is an enlarged portion of FIG. 3.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

With reference to FIG. 1, an exemplary assembly constructed inaccordance with the teachings of the present disclosure is generallyindicated by reference numeral 10. In the particular example provided,the assembly 10 is a an axle assembly, but it will be appreciated thatthe teachings of the present disclosure have application to otherassemblies having a housing and two components that are movably engagedto one another and received in the housing, including other drivelinecomponents such as power take-off units.

The assembly 10 has a housing 12, an input pinon or first component 14and a ring gear or second component 16. The housing 12 defines a cavity18 into which the input pinion 14 and the ring gear 16 are received. Theinput pinion 14 is supported for rotation relative to the housing 12about a first axis 20 by a pair of pinion bearings 22. The ring gear 16can be supported for rotation relative to the housing 12 about a secondaxis 30 and can be meshingly engaged with the input pinion 14. In theexample provided, the ring gear 16 is fixedly coupled to a differentialcase 32, and the differential case 32 is supported for rotation relativeto the housing 12 about the second axis 30 by a pair of differentialbearings 34. The input pinion 14 and the ring gear 16 can be spiralbevel gears, such as hypoid gears.

With reference to FIG. 2, a method for forming the assembly 10 (FIG. 1)is illustrated. Briefly, the method entails the superfinishing of a pairof workpieces to form a pair of components, and the subsequent mountingof the components into a housing where the components are engaged to oneanother and are movable relative to one another in a predeterminedmanner.

With reference to FIGS. 2 through 4, the method begins at bubble 50 andproceeds to block 52 where a first workpiece 114 and a second workpiece116 are provided. In the example provided, the first workpiece 114 is ahypoid (spiral bevel) pinion gear having “unfinished” pinion gear teeth,while the second workpiece is a hypoid (spiral bevel) ring gear having“unfinished” ring gear teeth.

The method can proceed to block 54, where the first and secondworkpieces 114 and 116 are mounted into a superfinishing machine 120 andthereafter the superfinishing machine 120 is operated so that asuperfinishing operation is performed on the first and second workpieces114 and 116 while they move relative to one another and engage oneanother in a manner that produces relative sliding motion between thefirst and second workpieces 114 and 116. The superfinishing operation isconfigured to “finish” the engaging surfaces of the first and secondworkpieces 114 and 116 to thereby form “finished” surfaces on the firstand second components 14 and 16 (FIG. 1). It will be appreciated thatthe superfinishing operation is configured to provide the matingsurfaces of the first and second components 14 and 16 (FIG. 1) with adesired surface finish as well as a desired degree or level ofconformity between the engaging surfaces. It will also be appreciatedthat other machining operations may be performed on the first component14 (FIG. 1) and/or second component 16 (FIG. 1) on surfaces other thanthe engaging surfaces of the first and second components 14 and 16(FIG. 1) after the completion of the superfinishing operation.

In the example provided, the superfinishing machine 120 can be generallysimilar to a lapping machine and the superfinishing operation isintended to “finish” the portions of the pinion and ring gear teeth thatcontact one another during operation of the assembly 10. Thesuperfinishing machine 120 can include a first spindle 122, which isrotatable about a first machine axis 124, and a second spindle 126 thatis rotatable about a second machine axis 128. The first and secondmachine axes 124 and 128 can be oriented relative to one another in amanner that is similar to the orientation of the first and second axes20 and 30 (FIG. 1) in the assembly 10 (FIG. 1). The first workpiece 114can be mounted to the first spindle 122 for rotation about the firstmachine axis 124. The second workpiece 116 can be mounted to the secondspindle 126 for rotation about the second machine axis 128 and can bemeshingly engaged with the first workpiece 114.

The superfinishing operation can be performed in various different ways.For example, the superfinishing operation can comprise chemicalpolishing, electro-polishing, chemically-accelerated surface finishingwith tribochemical film deposition and combinations thereof.

Chemical polishing could employ the use of a non-abrasive fluid, such asa non-abrasive fluid employed in an isotropic superfinishing operation,on/between the first and second workpieces 114 and 116 as they areengaged to one another and moved relative to one another in a mannerthat produces relative sliding motion between the first and secondworkpieces 114 and 116. The fluid can interact with the material on thesurfaces of the first and second workpieces 114 and 116 to create aconversion coating on the surfaces of the first and second workpieces114 and 116. As the first and second workpieces 114 and 116 are engagedto one another and are moved relative to one another (i.e., sliderelative to one another) during the superfinishing operation, therubbing of the first and second workpieces 114 and 116 against oneanother will wipe away parts of the conversion coating from peaks on thesurfaces of the first and second workpieces 114 and 116, therebyreducing the relative height of the peaks. Continued exposure of thefirst and second workpieces 114 and 116 to the fluid will permit theexposed portions (on the peaks) of the first and second workpieces 114and 116 to interact with the fluid and (re) form the conversion coating.The repeated formation and removal of the conversion coating over thepeaks or high spots on the first and second workpieces will eventuallyremove sufficient material from the engaging surfaces of the first andsecond workpieces 114 and 116 to reduce the surface roughness of thesesurfaces, as well as improve the degree or level of conformity betweenthese surfaces, and thereby form the first and second components 14 and16 (FIG. 1). One suitable supplier for such a fluid is REM SurfaceEngineering of Southington, Connecticut.

Electropolishing could employ an electrolyte fluid on/between theengaging surfaces of the first and second workpieces 114 and 116 and theprovision of electric energy to the first and second workpieces 114 and116 that permits one of the first and second workpieces 114 and 116 tofunction as an anode and the other one of the first and secondworkpieces 114 and 116 to function as a cathode. Contact between thepeaks or high spots on the first and second workpieces 114 and 116 whilethe first and second workpieces 114 and 116 are moved (slid) relative toone another can cause the peaks or high spots to dissolve in theelectrolyte fluid at a relative faster rate than the portions of thesurfaces of the first and second workpieces 114 and 116 that surroundthe peaks or high spots to reduce the surface roughness of thesesurfaces and improve the degree or level of conformity between thesesurfaces and thereby form the first and second components 14 and 16(FIG. 1).

Chemically-accelerated surface finishing with tribochemical filmdeposition could employ a coating fluid on/between the engaging surfacesof the first and second workpieces 114 and 116. The engaging surfaces ofthe first and second workpieces 114 and 116 can act as burnishing toolsagainst one another to thereby reduce the surface roughness of thesesurfaces and improve the degree or level of conformity between thesesurfaces, as well as apply pressure on the fluid on the engagingsurfaces that causes the fluid to convert to a coating having desiredfriction characteristics to thereby form the first and second components14 and 16 (FIG. 1). One suitable supplier for such a fluid is AppliedNano Surfaces AB of Uppsala, Sweden

The superfinishing operation “finishes” the surfaces the portions of thefirst and second workpieces 114 and 116 that engage (slide on) oneanother to thereby form the first and second components 14 and 16 (FIG.1). The first and second components 14 and 16 (FIG. 1) can be removedfrom the superfinishing machine 120 as a matched set.

With reference to FIGS. 1 and 2, the method can proceed to block 56where as a matched set the first and second components 14 and 16 can beengaged to one another and mounted in the housing 12 for movementrelative to one another in a predetermined manner. As described above,the pinion gear or first component 14 can be mounted to the housing 12for rotation about the first axis 20 and the ring gear or secondcomponent 16 can be meshed with the input pinion 14 and mounted to thehousing 12 for rotation about the second axis 30.

While the first and second components 14 and 16 have been illustratedand described as being rotatable about two transverse axes, it will beappreciated that the first and second axes 20 and 30 could be configuredin a different manner, and could intersect one another or could beparallel to one another. Moreover, the first and second components 14and 16 need not have teeth that meshingly engage one another but rathercould have surfaces that engage one another in another manner, such asrolling contact. Furthermore, movement of the first and secondworkpieces relative to one another in the predetermined manner cancomprise translating one of the first and second workpieces along anaxis of the other one of the first and second workpieces.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

What is claimed is:
 1. A method for forming an assembly having a housingand first and second components, the first and second components beingmovable relative to one another in the housing, the method comprising:mounting a first workpiece for rotation about a first axis; mounting asecond workpiece in meshing engagement with the first workpiece and forrotation about a second axis; rotating the first workpiece about thefirst axis to drive the second workpiece about the second axis toproduce relative sliding motion between the first and second workpieces;performing a superfinishing operation on the first and second workpiecesduring the production of relative sliding motion between the first andsecond workpieces to form the first and second components, respectively,wherein the superfinishing operation does not comprise a lappingoperation; and mounting the first and second components in the housingsuch that the first and second components are meshingly engaged to oneanother and are rotatable relative to the housing about the first andsecond axes, respectively; wherein a non-abrasive fluid is employed inthe superfinishing operation; and wherein the superfinishing operationcomprises chemical polishing, electro-polishing, chemically-acceleratedsurface finishing with tribochemical film deposition and combinationsthereof.
 2. The method of claim 1, wherein one of the first and secondcomponents is a ring gear and the other one of the first and secondcomponents is a pinion gear.
 3. The method of claim 2, wherein the ringgear and the pinion gear are spiral bevel gears.
 4. The method of claim2, wherein the assembly is a power take-off unit or an axle assembly.